The present invention relates to a seal pattern of a liquid crystal display ("LCD"), and more particularly, to a seal pattern of an LCD in which a high quality seal pattern can be repeatedly manufactured.
2. Description of the Related Art
LCD's that are widely used in very small portable TV's and laptop or notebook-type computers consume less power than conventional cathode ray tube displays. These LCD's also make such devices lighter and thinner. Thus, LCD's are finding more and more use. A conventional LCD includes an upper substrate having a common electrode, a lower substrate having pixel electrodes and thin film transistors, metal wiring, etc., for activating the pixel electrodes, a seal pattern for sealing the upper and lower substrates with a predetermined gap therebetween, and a liquid crystal material filling the space between the upper and lower substrates.
FIG. 1 is a plan view of a conventional LCD. An rectangular active area 11 is formed on a central part of a lower substrate 12 made of transparent glass. Pixel electrodes and thin film transistors, metal wiring, capacitors, etc. , for activating the pixel electrodes are provided on the active area 11. A seal pattern 13 is also formed on the lower substrate 12 about the active area 11, spaced a predetermined distance therefrom.
A liquid crystal injection port 14 for injecting the liquid crystal material is provided on one side of the seal pattern 13 as seen in FIG. 1. A seal bar 15 is formed between the liquid crystal injection port 14 and the active area 11. An end seal 16 is provided for sealing the injection port 14. The seal bar 15 prevents the end seal 16 from penetrating into the interior of seal pattern 13. The seal pattern 13, seal bar 15, and end seal 16 are formed with a predetermined height corresponding to the gap between the upper and lower substrates. The seal pattern 13, seal bar 15, and end seal 16 are formed by an adhesive insulating epoxy or the like.
The assembly process of the conventional LCD after forming the seal pattern 13 and the seal bar 15 on the lower substrate is as follows.
The upper substrate (not shown) having a common electrode is positioned and mounted on the lower substrate 12 having seal pattern 13 and seal bar 15 formed thereon. A predetermined amount of pressure is applied to the upper substrate and lower substrate 12 and heat is applied to harden material constituting the seal pattern 13 and seal bar 15. The liquid crystal is then injected through the liquid crystal injection port 14 after a vacuum is created in the space between the upper and lower substrates. Lastly, a cleaning process to remove loose epoxy debris is performed after sealing the liquid crystal injection port 14 with end seal 16.
In the above-described seal pattern process for a conventional LCD, the upper substrate is pressed during a heat treatment step after the upper substrate has been mounted on the lower substrate. At this time, pressure is typically not evenly applied to the seal pattern, causing the gap between the substrates to be irregular. This diminishes the operational reliability of the LCD.
In addition, the seal pattern integrity can be broken be dirt, chemicals, or other contaminants on the seal pattern, or the upper and lower substrates when the gap between the substrates is in a vacuum state. This again diminishes the quality of the LCD.
Finally, the end seal may leak during the cleaning process (typically a brushing process), again diminishing the quality of the LCD. Specifically, the integrity of the end seal is dependent on secure adhesion between the end seal and the injection port. This adhesion is susceptible to being disrupted during the cleaning process.